The present invention relates to the creation of proximity sound effects and, in particular, to an apparatus and method for creating proximity sound effects in audio systems.
The present application is related to the state of the art in channel-based surround sound audio reproduction and object-based scene rendering. There exist several surround sound systems that reproduce audio with a plurality of loudspeakers placed around a so called sweet spot. A sweet spot is the place where the listener should be positioned to perceive an optimal spatial impression of the audio content. Most popular systems that work like that are regular 5.1 or 7.1 systems with 5 or 7 loudspeakers positioned on a circle or sphere around the listener and a low frequency effect channel. The audio signals to feed the loudspeakers are either created during the production process by a mixer (e.g. motion picture sound track) or are generated in real-time, e.g. in interactive gaming scenarios.
State-of-the-art surround sound systems can produce sounds placed nearly in any direction with respect of a listener positioned in the sweet spot of a system. What is not possible to reproduce with existing 5.1 or 7.1 surround sound are auditory events that the listener perceives in a close distance to his head. Several other spatial audio technologies like Wave Field Synthesis (WFS) or Higher Order Ambisonic (HOA) systems are able to produce so called focused sources, which can create that proximity effect using a high number of loudspeakers to concentrate acoustic energy at a steerable position relative to the speakers.
In particular, in the state of the art, several algorithms are used to place auditory events around the listener. Wave Field Synthesis systems using a much larger number of loudspeakers than regular surround sound systems are able to position auditory events outside and even inside the room [1, 2]. The sources which are positioned inside the room are usually called “focused sources” because they are calculated to focus sound energy at a specific spot located within the loudspeaker array. Typical WFS systems comprise an array of loudspeakers around the listener. However, the amount of loudspeakers needed usually is very high leading to the use of expensive loudspeaker panels with small loudspeaker drivers.
Another approach to reproduce focused sources that have similar characteristics as using WFS focus sources is Higher Order Ambisonics (HOA) [3].
In [4], a device is described utilizing a plurality of loudspeakers for steering sound to a specific point in space by using individually calculated delays for all loudspeakers. There also exists an approach called “time reversal mirror” [5] to optimize the effect of focused source by increasing the difference in sound level between the focus point and its surrounding area.
In the known art, a WFS system is combined with regular, but larger and more powerful speakers to be able to combine the high resolution of sound localization that WFS provides with the powerful sound levels that typical live public address (PA) systems can provide. In [6], a combination of a WFS system with additional large single loudspeakers is described where the additional loudspeakers are meant to support the WFS system in terms of sound level. The delay between those two systems is set so that the sound of the WFS speakers arrives at the listener position before the sound of the additional loudspeakers. This is done in order to use the precedence effect; the listeners will localize the source according to the sound of the WFS system with the higher localization resolution while the additional loudspeakers will help increase the perceived loudness without significantly affecting the localization perception of the sound source.
While using a full WFS system at home is not feasible due to the high number of individual loudspeakers needed, sound bars containing a multitude of speakers are already available and can be used to play back focused sources.
However, while WFS can reproduce several types of audio objects (e.g. point sources and plane waves [1]), the high resolution of localization for sources farer away is usually not required at home.
It would be appreciated, if improved concepts for creating proximity sound effects would be provided.